【作者】 江婵；

【导师】 涂伟萍；

【作者基本信息】 华南理工大学 ， 化学工程， 2012， 博士

【摘要】 低介电常数、高品质因数微波介质陶瓷材料的合成及研究是近年来的研究热点，本文制备了Sm₂SiO₅陶瓷，Sm₄（SiO₄）₃陶瓷，Nd₂SiO₅陶瓷，Al₂O₃-TiO₂陶瓷，MgTiO₃-CaTiO₃陶瓷和（Zn,Mg）TiO₃-TiO₂陶瓷，并用XRD、SEM、EDS和TG-DTA等多种分析测试手段及开腔谐振测试方法，研究了这些低介陶瓷的相组成、致密度和微观结构等对材料介电性能的影响，探索介电性能的演变规律，并将（Zn,Mg）TiO₃-TiO₂复合陶瓷用于制备多层片式陶瓷电容器（MLCC）。1.研究以非化学计量比效应合成新型的单相Sm₂SiO₅低介电常数微波陶瓷。当Sm₂O₃/SiO₂摩尔比为1:1.05，在1350℃烧结4h，可得到纯的单斜Sm₂SiO₅相。随着温度的升高，可以得到少量的六方Sm₄（SiO₄）₃相，并且随着温度的升高，Sm₂SiO₅陶瓷样品的相对密度随之增加。Sm₂SiO₅陶瓷在1500℃下烧结后，有优良的介电性能：εr=8.5,Q×f=64878.71GHz和τf=-37.64ppm/℃。Sm₂SiO₅陶瓷材料有着较宽的烧成温度范围和小的负温度系数，因此可以作为优良的介电材料用于毫米波通讯装置中。2.研究以非化学计量比效应合成新型的单相Sm₄（SiO₄）₃低介高频微波陶瓷。发现Sm₂O₃-xSiO₂（1.425≤x≤1.6）在1350-1600℃下烧结四个小时，均能得到纯六方Sm₄（SiO₄）₃相。当x=1.5时，样品的介电性能: εr=9.03，Q×f=17470.76GHz （12.40GHz）和τf=-24.4ppm/℃。Sm₄（SiO₄）₃陶瓷材料有着很宽的烧成温度范围和较小的负温度系数。3.研究以非化学计量比效应合成新型的单相Nd₂SiO₅低介电常数微波陶瓷。当Nd2O₃/SiO₂摩尔比为1:1.05，在1450℃下烧结时，第二相六方Nd₄Si₃O₁₂相消失，纯单斜Nd₂SiO₅相出现。随着烧温的升高，Nd₂SiO₅陶瓷的相对密度升高。Nd₂SiO₅陶瓷在1500℃下烧结，介电性能: εr=7.94，Q×f=38800GHz, τf=-53ppm/℃。高自谐振频率导致低的介电常数和低的Q×f值。Nd₂SiO₅陶瓷有较宽的烧成温度范围，它们有潜力应用在微波被动元器件中。4.使用新颖的水基溶胶凝胶法合成0.9Al₂O₃-0.1TiO₂包覆性纳米颗粒，用二（2-羟基丙酸）二氢氧化二铵合钛（TALH）为钛盐水基前驱体，与传统的钛醇盐sol-gel法相比，不需要乙醇做溶剂体系。本文对其制备条件进行了优化。α-Al₂O₃和金红石相晶粒生长指数（n）各为2.5和4，晶粒生长活化能分别为100kJ/mol和107kJ/mol。沿着晶界扩散后形成的缝合线，纳米层通过高温自组装途径生长，其微波介电性能：εr=10.4, Q×f=18000GHz, τf=-10.8ppm/℃（在1300℃烧结）和εr=13, Q×f=32000GHz, τf=45ppm/℃（又在1100℃下退火10h）。5.采用固相法合成MgTiO₃-CaTiO₃复合陶瓷，加入CaTiO₃用来调节MgTiO₃过负的频率温度系数，加入3ZnO-B₂O₃可以促进体系的烧结。（a） MgTiO₃-CaTiO₃陶瓷随着CaTiO₃掺入量的增加，体系的介电常数和温度系数随之增加，品质因数随之下降，样品的介电性能与微观结构和晶相转变有着密不可分的联系。0.97MgTiO₃-0.03CaTiO₃在1300℃下具有优良的微波介电性能: εr=18.23, Q×f=76529GHz （7.37GHz）和τf=-34.68ppm/°C。（b）适量的ZB掺杂0.97MgTiO₃-0.03CaTiO₃，在降低烧温的同时，并没有明显恶化体系的介电性能。0.97MgTiO₃-0.03CaTiO₃+2wt.%ZB在1225℃下具有优良的微波介电性能: εr=17.96, Q×f=79346GHz （7.47GHz）和τf=-34.93ppm/°C。6.采用固相法合成（Zn,Mg）TiO₃-TiO₂复合陶瓷，加入TiO₂用来稳定（Zn, Mg）TiO₃六方相和调节谐振频率温度系数，加入3ZnO-B₂O₃可以促进体系的烧结，体系遵循液相烧结机理，烧结过程中有明显的晶界运动。SEM和EDS显示，在烧结过程中，游离的（Zn, Mg）TiO₃颗粒会在晶界上产生偏析甚至脱溶出来分凝在晶界上。SnO₂因为能阻止晶界扩张而被用做晶粒细化剂。样品的介电性能与微观结构和晶相转变有着密不可分的联系，我们发现（Zn, Mg）TiO₃-0.25TiO₂+1.0wt.%3ZnO-B2O₃+0.1wt.%SnO₂（ZMTZBS，1000°C）呈现优良的介电性能: εr=27.7, Q×f=65494GHz （6.07GHz）和τf=-8.88ppm/°C。7.用介电性能优良的ZMTZBS陶瓷粉料成功制造了具有良好电性能的多层片式陶瓷电容器。我们发现：随着电容量增加，电容器的自谐振频率和等效串联电阻相应减少，而品质因数随着频率或电容量增加而减少。更多还原

【Abstract】 Preparation of microwave ceramic materials with low dielectric constant and highquality factor has become a research focus in recent years. In this paper, Sm₂SiO₅ceramics,Sm₄（SiO₄）₃ceramics, Nd₂SiO₅ceramics, Al₂O₃-TiO₂ceramics, MgTiO₃-CaTiO₃ceramicsand （Zn, Mg）TiO₃-TiO₂ceramics were synthesized. The phase composition, density andcrystal microstructure of ceramic materials with low dielectric constant were analyzed byXRD, SEM, EDS, TG-DTA and so on. Microwave dielectric properties were tested byHakki-Coleman opened resonator method. The relationship between microstructure andmicrowave dielectric properties was also investigated. The evolution of dielectric propertieswas discussed.（Zn,Mg）TiO₃-TiO₂composite ceramics were applied to manufacturemultilayer ceramic capacitors （MLCC）.1. Sm₂SiO₅ceramics were synthesized by solid phase method. The pure monoclinicSm₂SiO₅phase could be obtained when Sm₂O₃/SiO₂=1:1.05at1350℃. The hexagonalSm₄（SiO₄）₃second phase occurred as temperature increased. The densification of Sm₂SiO₅ceramics increased with increasing temperature. The Sm₂SiO₅ceramics sintered at1500℃exhibited microwave dielectric properties: a dielectric constant （εr） of8.5, a quality factor Q×fof64878.71GHz and a temperature coefficient of resonant frequency （τf） of-37.64ppm/℃.Sm₂SiO₅ceramics had a wide temperature region and small negative τfvalue. They arepromising candidate materials for millimeter-wave devices.2. Sm₄（SiO₄）₃ceramics were synthesized by solid phase method. The pure hexagonalSm₄（SiO₄）₃phase could be obtained when Sm₂O₃/SiO₂=1:1.425-1.6at1350℃-1600℃for4h. when Sm₂O₃/SiO₂=1:1.5at1550℃, Sm₄（SiO₄）₃ceramics exhibited microwave dielectricproperties: a dielectric constant （εr） of9.03, a quality factor Q×f of17470.76GHz （12.40GHz）and a temperature coefficient of resonant frequency （τf） of-24.4ppm/℃. Sm₄（SiO₄）₃ceramics had a wide temperature region and small negative τfvalue.3. Nd₂SiO₅ceramics were synthesized by solid phase method. The hexagonal Nd₄Si₃O₁₂second phase disappeared and the pure monoclinic Nd₂SiO₅phase could be obtained when themolar ratio of Nd2O₃/SiO₂was1:1.05at1450℃. The relative density of Nd₂SiO₅ceramicsincreased with increasing temperature. The Nd₂SiO₅ceramics sintered at1500℃exhibitedmicrowave dielectric properties: a dielectric constant （εr） of7.94, a quality factor （Q×f） of38800GHz and a temperature coefficient of resonant frequency （τf） of-53ppm/℃. Highresonant frequency led to a low dielectric constant and low Q×f value. Nd₂SiO₅ceramics had a wide temperature region. They are promising candidate materials for microwave passivecomponents.4. The0.9Al₂O₃-0.1TiO₂nano-particles were synthesized by novel water-based sol-gelmethod. Compared with the traditional sol-gel method using titanium alcohol salt, this methoddid not need ethanol solvent system using TALH as titanium salt water-based precursor body.The preparation condition of0.9Al₂O₃-0.1TiO₂nano-particles was optimized. The graingrowth exponent （n） values were2.5and4for α-Al₂O₃and rutile, respectively. The activationenergies of grain growth were estimated to be100and107kJ/mol for α-Al₂O₃and rutile.Along suture line emerging after grain boundary diffusion, the nano-sheets of Al₂O₃-TiO₂grew through high temperature self-assembly way. The microwave dielectric behaviors of0.9Al₂O₃-0.1TiO₂ceramics were εr=10.4, Q×f=18000GHz, τf=-10.8ppm/℃（as preparedat1300℃）, and εr=13, Q×f=32000GHz, τf=45ppm/℃（post-annealed at1100℃for10h）.5. MgTiO₃-CaTiO₃composite ceramics have been prepared via the solid-phase synthesismethod. CaTiO₃was employed to tone negative temperature coefficient of resonant frequency（τf） of MgTiO₃,3ZnO-B2O₃was effective to promote sintering.（a） With the content of CaTiO₃increasing, dielectric constant and temperature coefficientof MgTiO₃-CaTiO₃ceramics increased, and quality factor reduced. The dielectric propertiesdepended on microstructure and grain phase transition closely. Microwave dielectricbehaviors of0.97MgTiO₃-0.03CaTiO₃ceramics were: εr=18.23, Q×f=76529GHz （7.37GHz）, τf=-34.68ppm/°C （at1300℃）.（b） Right amount of ZB doping0.97MgTiO₃-0.03CaTiO₃, led to the decrease in thesintering temperature, and the dielectric properties had no significant deterioration.Microwave dielectric behaviors of0.97MgTiO₃-0.03CaTiO₃+2wt.%ZB ceramics were: εr=17.96, Q×f=79346GHz （7.47GHz）, τf=-34.93ppm/°C （at1225℃）.6.（Zn, Mg）TiO₃-xTiO₂composite ceramics were prepared via solid-phase synthesismethod. TiO₂was employed to tone temperature coefficient of resonant frequency （τf） andstabilized hexagonal （Zn, Mg）TiO₃phase.3ZnO-B₂O₃was effective to promote sintering. Themovement of grain boundary was obvious because of the liquid phase sintering. SEM andEDS showed that segregation and precipitation of dissociative （Zn, Mg）TiO₃grains occurredat grain boundary during sintering. SnO₂was used as inhibitor to prevent the grain boundaryfrom moving. The dielectric behaviors of specimen strongly depended on structural transitionand microstructure. We found that1.0wt.%3ZnO-B₂O₃doped （Zn, Mg）TiO₃-0.25TiO₂ceramics with0.1wt.%SnO₂additive displayed excellent dielectric properties （at1000°C）: εr =27.7, Q×f=65494GHz （at6.07GHz） and τf=-8.88ppm/°C.7. The above-mentioned material was applied successfully to make multilayer ceramiccapacitors （MLCC）, which exhibited excellent electrical properties. The self-resonancefrequency （SRF） and equivalent series resistance （ESR） of capacitor decreased withcapacitance increasing, and the quality factor （Q） of capacitor reduced as frequency orcapacity increased.更多还原